The majority of females are simply not capable of the concept of responsibility. Not really their fault. It's what the are. They are like wild sheep that need taming. The mistake lies with men believing otherwise. When we accept that simple fact it is astonishing how much it all makes sense.
Most men don't want a super model, but want someone with a healthy shape and female dimorphism which is slim/normal and gracile. Until men in general raise their standards on what they will fuck or at least talk to a big girl (not huge o'beasts but say 20-35lbs overweight) and convince her to workout, this cycle will continue. Also women not encouraging their friends to get to a healthy BMI is an issue as well. Most women hate competition and will lie to their fat friends that they look great to stay in a certain place in life. Most guys will tell their male friend, brother, dad etc that they look bad with a pot belly, double chin, moobs etc. Men are honest with each other women aren't.